Elkan Nathan Adler (1861–1946) was an Anglo-Jewish author, lawyer, historian, and collector of Jewish books and manuscripts. Adler's father was Nathan Marcus Adler, Chief Rabbi of the British Empire. He travelled extensively and built an enormous library, particularly of old Jewish documents. Adler was among the first to explore the documents stored in the Cairo Genizah. During his visits to Cairo in 1888 and 1895 Adler collected and brought over 25,000 Genizah manuscript fragments back to England.
In 1921 he published a summary Catalogue of Hebrew Manuscripts in the Collection of E. N. Adler in which he described over 4,500 manuscripts in his collection. Adler collected some 30,000 printed books in Judaica. Unfortunately for him, a business associate's embezzlement forced him to sell most of his library to the Jewish Theological Seminary of America in New York City and Hebrew Union College in Cincinnati in 1923. Moreover, Adler agreed to bequeath his subsequent acquisitions to the Jewish Theological Seminary upon his death.
Adler published many books about his travels and on his extensive collections, including About Hebrew Manuscripts (1905), A Gazetteer of Hebrew Printing (1917); Jews in Many Lands (1905); Auto de Fe and Jew (1908); History of the Jews of London (1930); Jewish Travellers (1930, repr. 1966); and articles on the Samaritans and on the History of the Jews in Egypt and Persia. Adler was extremely active in English-Jewish communal affairs, especially in education, and was an ardent Zionist; he was an early member of the Hovevei Zion in England. Per his will, his personal archives are now at the library of the Jewish Theological Seminary of America.